Oxygen saturation in depth

Technically what the previous page described is 'fractional' oxygen saturation. That is the amount of oxygen the haemoglobin is carrying as a percentage of the maximum possible that that much haemoglobin could carry. This is 1.39 millilitres of oxygen per gram of haemoglobin.

However in practice there will always be some haemoglobin that is dysfunctional or combined with something other than oxygen and so is not available to carry oxygen. 'Functional' oxygen saturation is defined as the amount of oxygen that the haemoglobin is carrying as a percentage of the maximum that that particular specimen could carry. This is usually about 1.34 millilitres of oxygen per gram of haemoglobin.